Abstract: The quality requisites of shellfishes are primarily dependent on the water quality, assuring a healthy product and a safe consumption. Water (moisture) content of five species from two different environments was conducted for a period of one year (July, 2010-June, 2011) for this purpose. Among the most exploitable and economically important Egyptian species, three brackish (the bivalves Cerastoderma glaucum, Fulvia fragilis and the gastropod Thais carinifera) and two salt water (the bivalves Donax semistriatus and Donax trunculus) shellfishes were chosen. Estimation on monthly basis revealed the incompatibility of moisture content with spawning period. Present results proved that water content varied according to the environmental factors rather than spawning seasons. Marine species had lower demand of water than brackish species. The differences in the average of the body water content between genera [Donax sp. (0.13), C. glaucum (0.75), F. fragilis (2.35) and T. carinifera (3.68)] was greater than that within the same genus [D. semistriatus (0.10) and D. trunculus (0.16)]. The gastropod T. carinifera had higher water content than the bivalves. Hierarchical clusters analysis was a good tool to differentiate moisture content between genera, as well as between species from different environments. The present study put in the perception of the probability of use water content in discrimination and classification between species.